Thermostatic control structure

ABSTRACT

A bimetal strip operated control comprises a switch housing and a frame supporting the strip and rigidly attached to the housing with an appreciable air gap between the housing proper and the frame. A plate of insulating material of the type which is dimensionally affected by its moisture content is disposed in the gap between the housing and frame so as to provide electrical insulation intermediate the switch terminals, projecting from a side of the housing, and the frame. The spacing of the frame from the housing proper and the thickness of the insulation member is such as to permit expansion and contraction of the insulation member without affecting the spatial relationship of the frame, including the bimetal strip, and housing.

United States Patent [191 Heiser et al.

[ THERMOSTATIC CONTROL STRUCTURE [75] Inventors: E. Franklin Heiser; Andrew Kulick,

both of Columbus, Ohio [73] Assignee: Ranco Incorporated, Columbus,

Ohio

[22] Filed: Mar. 7, 1973 [21] Appl. No.: 338,836

[4 1 Apr. 2, 1974 Primary Examiner-Hemard A. Gilheany Assistant Examiner-F. E. Bell Attorney, Agent, or Firm-Watts, l-loffmann, Fisher & Heinke [57] ABSTRACT A bimetal strip operated control comprises a switch housing and a frame supporting the strip and rigidly attached to the housing with an appreciable air gap between the housing proper and the frame. A plate of insulating material of the type which is dimensionally affected by its moisture content is disposed in the gap between the housing and frame so as to provide electrical insulation intennediate the switch terminals, projecting from a side of the housing, and the frame. The spacing of the frame from the housing proper and the thickness of the insulation member is such as to permit expansion and contraction of the insulation member without affecting the spatial relationship of the frame, including the bimetal strip, and housing.

5 Claims, 3 Drawing Figures THERMOSTATIC CONTROL STRUCTURE BACKGROUND OF THE INVENTION Thermostatic controls of air tempering equipment has been provided comprising a switch housing having a frame attached thereto which carries a thermostatic element, such as a bimetal, operatively connected with the switch in the housing. Examples of such thermostatic controls are disclosed in U.S. Pat. Nos. 2,229,612, 2,427,946 and 3,546,652.

U.S. Pat. No. 3,546,652 discloses the use of a material composed of a thermoplastic or thermoset resin witha filler of fibres formed of asbestos, rock wool and the like, for providing an electrical and heat insulating wall between the housing and frame. The patent also discloses a hood formed by outer portions of the insulating wall to direct air flow over the bimetal thermostatic element. The central portion of the insulating wall is continuous and is closely confined between the confronting surfaces of the switch housing. and the ing character of the switch because the spatial relation of the bimetal relative to the switch is shifted.

THE PRESENT INVENTION The present invention provides a thermostatic control comprising a switch housing, a thermostatic element on a frame attached to the switch housing, and a sheet-like insulating member relatively loosely retained between the principal confronting surfaces of the housing and frame,-the frame being spaced from the confronting wall of the switch housing by rigid, dimensionally stable spacing means, and the insulation member having an aperture for receiving the spacing means, the

thickness of the insulating material being appreciably less than the space between the confronting surfaces of the housing and frame so that expansion and contraction of the insulating material does not result in distortion of the space between the switch and the frame supporting the switch operating bimetal.

' A further object of the invention is the provision of a thermostatic control mechanism of the character mentioned in which the sheet-like insulating member has a central opening therethrough which provides a substantial air space between the major portions of the confronting surfaces of the switch housing and the frameattached thereto. The air space admits a flow of air between the switch housing and bimetal supporting frame, thereby dissipating heat which might otherwise accumulate in the switch housing and migrate to the bimetal.

Other objects and advantages of the invention will be apparent from the following description of a preferred form of the invention, reference being made to the accompanying drawings wherein:

FIG. 1 is a side elevational viewv of a thermostatic control embodying the invention;

FIG. 2 is a sectional view taken substantially along line 22 of FIG. 1; and

FIG. 3 is a partial sectional view taken substantially along lines 3-3 of FIG. 2. v

A thermostatically operated control mechanism 10 is shown which is particularly suitable for controlling the operation of an electrically powered air' tempering apparatus, such as an electric powered room air conditioner unit, not shown. The control mechanism 10 comprises a suitable snap acting switch, not shown, enclosed in a relatively rigid housing 11. The housing 11 preferably comprises a box-like body 12, the open side of which is substantially closed by a cover T3. The body and cover are preferably formed of a suitable dimensionally stable or rigid dielectric thermosetting material, and two switch terminals 14 project from one side of the housing. The details of the switch in the housing are not shown as any suitable types may be utilized. Suffice to say, the operation of the switch is effected by a reciprocable plunger 15 which projects from the housing 11 through an opening formed in the cover 13 and having a ridge or flange 16 therearound. The snap mechanism for the switch is the type which constantly maintains an outward or upward bias on the plunger 15, as viewed in the drawings. I

The plunger 15 is adapted to be moved into the housing to operate the switch by a strip of bimetal 17. The bimetal 17 is supported by a frame 18 attached to the housing 11. The frame 15 includes a strip-like bracket 20 by which the switch 11 can be bolted or otherwise attached to the equipment it is to control. Also, the frame 18 carries a rotatable adjusting shaft 21 which is adapted to receive a knob, not shown, by which the shaft can be conveniently rotated by the user of the equipment. The details by which the bimetal 17 is supported on the frame 18 are not essential to the understanding of the present invention and are not further described. Similar structure is more fully described in the aforementioned U.S. Pat. No. 3,546,632.

The frame 18 is comprised of a relatively rigid metal strip having a flat base section 23 which abuts bosses 24,25,26 formed on the cover 13 of the switch housing 12. The frame 18 is secured to the bosses 24 and 26 by rivets 30,31 extending through openings through the frame section 23 and the respective bosses. The frame section 23 has an opening 32 through which the flange 16 and the plunger 17 project when the frame is assembled to the housing as just described. The bosses 24,25,26 rigidly space the frame from the housing wall formed by the cover 13 so that the spatial relation of the bimetal strip and the switch mechanism remain constant.

A box-like hood 33 is carried by the housing 12 and is assembled to the control when the frame 18 and switch housing 11 are joined. The hood 33 includes a bottom wall 34 and three side walls 35,36,37. The hood erwise and expands and contracts as its moisture content increases and decreases. lt'is desirable for the use proposed because'it is relatively inexpensive, is conveniently fabricated and provides good electrical insulation. In the form of the invention shown, the hood 33 not only channels the flow of air over the bimetal strip but also provides an electrical barrier between the terminal members 14 and the frame section 23. According to the present invention, the wall 34 of the hood 33 is supported so that a portion of the wall 34 thereof is interposed between the switch terminals 14 and the frame section 23 so as to provide an electrical barrier and yet the material forming the wall may expand and contract without affecting the spatial relationship between the bimetal strip and the switch operating plunger. This is accomplished by forming the heights of the bosses 24,25,26 from the outer surface of the cover 13 at least asgreat as the possible maximum thickness of the hood wall 34. The central portion of the wall 34 has a rectangular opening 40 formed therein which is slightly less than the outer dimensions of the cover. A pair of notches 41,42, are formed at the ends of the opening 40 and the edges of the notches loosely surround the outer sides of the respective bosses 24,26. The edges of the notches 41,42 engage the sides of the bosses 24,26 and prevent escape of the wall34 from between the housing and frame and maintain the hood 33 substantially in position on the control. The mounting of the frame section 23 on the bosses 24,25,26' as minals and the frame.

We claim:

1. A thermostatic control mechanism comprising a switch housing, a metallic frame supporting a thermostatic element, means attaching a wall-like section of said frame to one wall of said housing including rigid boss means between said wall and said frame section to provide a predetermined spacing between said housing wall and frame section, and a sheet-like insulating member disposed between at least a portion of said wall 1 and said section of said frame, the maximum thickness described establishes a substantial air space between the cover 13 and the frame as seen at 43 whereby air may circulate between the frame and housing and dissipate heat which may develop by current passing through the switch mechanism.

The width of the opening 40 in the wall 34 is such that an edge portion 44 extends inwardly between the side edge of the housing cover 13 and the frame section 23 to provide an effective electrical barrier between the switch terminals 14 and the frame section.

It will be appreciated that if the hood 33 is not required, a plate-like insulating member corresponding to the hood wall 34 could be secured between the switch housing cover and the frame in the same manner as described with respect to the hood wall 34- thereby providing electrical insulation between the switch terof said insulation member being appreciably less than the spacing between said frame section and said housing wall.

2. A thermostatic control mechanism as set forth in claim 1 further characterized by said boss means comprising a plurality of bosses formed on said wall of said housing.

3. A thermostatic control mechanism as set forth in claim 1 wherein said bosses are located adjacent opposite ends of said wall and intermediate said'wall, respectively.

4. A thermostatic control as set forth in claim 1 further characterized in that said insulating member has apertures for receiving at least two of said bosses, and the edges of said apertures adapted to engage said bosses and prevent displacement of said member from between said frame and housing,

5. A thermostatic control mechanism comprising a switch housing including terminal means projecting from one side thereof, a metallic frame supporting a thermostatic element, means attaching a wall-like section of said frame to one wall of said housing including rigid boss means between said wall and said frame section to provide a predetermined spacing between said housing wall and frame section, and a sheet-like insulating member disposed between at least a portion of said wall and said section of said frame and extending between said frame and said terminal means projecting from said housing, the maximum thickness of said insulation member being appreciably less than the spacing between said frame section and said housing wall. 

1. A thermostatic control mechanism comprising a switch housing, a metallic frame supporting a thermostatic element, means attaching a wall-like section of said frame to one wall of said housing including rigid boss means between said wall and said frame section to provide a predetermined spacing between said housing wall and frame section, and a sheet-like insulating member disposed between at least a portion of said wall and said section of said frame, the maximum thickness of said insulation member being appreciably less than the spacing between said frame section and said housing wall.
 2. A thermostatic control mechanism as set forth in claim 1 further characterized by said boss means comprising a plurality of bosses formed on said wall of said housing.
 3. A thermostatic control mechanism as set forth in claim 1 wherein said bosses are located adjacent opposite ends of said wall and intermediate said wall, respectively.
 4. A thermostatic control as set forth in claim 1 further characterized in that said insulating member has apertures for receiving at least two of said bosses, and the edges of said apertures adapted to engage said bosses and prevent displacement of said member from between said frame and housing.
 5. A thermostatic control mechanism comprising a switch housing including terminal means projecting from one side thereof, a metallic frame supporting a thermostatic element, means attaching a wall-like section of said frame to one wall of said housing including rigid boss means between said wall and said frame section to provide a predetermIned spacing between said housing wall and frame section, and a sheet-like insulating member disposed between at least a portion of said wall and said section of said frame and extending between said frame and said terminal means projecting from said housing, the maximum thickness of said insulation member being appreciably less than the spacing between said frame section and said housing wall. 